Is the recent uptick in earthquakes in Saline County unusual? Here's what scientists think

·6 min read

After not having any recorded earthquakes until 2015, Saline County has been quite seismically active recently, as the past few months have seen.

People from across the county, including officials at multiple levels of government, and across the state, have been wondering what has been happening that Saline County has experienced such quakes in the past few months.

"All of us (commissioners) have lived here a long time, and this is unusual," said Commissioner Monte Shadwick during the Jan. 11, 2022 meeting of the Saline County Board of Commissioners. "People are asking questions."

Shadwick isn't wrong to say this is unusual, as Saline County had 138 magnitude 2 or higher quakes that the Kansas Geological Survey (KGS) recorded from Aug. 14 to Dec. 27, 2021. Of these 138, three of these were magnitude 4 or higher, the largest earthquakes recorded in Kansas during that time.

While she is not that concerned at this point, Michelle Barkley, the director of the Saline County Emergency Management Department, said there has been some very minor damage from at least one of these quakes.

"The 4.3 did cause some damage to Gypsum, broken pipes, things falling off shelves," Barkley said.

Previously: Kansas earthquake's epicenter is south of Salina, surprising Central Kansas residents

In speaking with officials at the United States Geological Survey, Barkley said this is something that can happen in most parts of the country.

"Unless you live in...Florida or North Dakota, there will always be shifting in the plates," Barkley said.

Rick Miller, a senior scientist at KGS, said studies in Kansas have shown seismicity to occur in the state. From 1977 to 1989, KGS, with funding from the U.S. Army Corps of Engineers and the Nuclear Regulatory Commission (NRC), deployed a network of seismometers across the state.

"(The Corps and NRC) were trying to do an appraisal of the seismicity (for) dam safety issues and the reactor safety issues associated with the...corps dams and with Wolf Creek Power Plant," Miller said.

This is one of the several seismometers the Kansas Geological Survey monitors in the state. Rick Miller, a senior scientist at KGS, said the network of seismometers in the state allows for any earthquake 1.8 magnitude or higher to be detected by the survey.
This is one of the several seismometers the Kansas Geological Survey monitors in the state. Rick Miller, a senior scientist at KGS, said the network of seismometers in the state allows for any earthquake 1.8 magnitude or higher to be detected by the survey.

With the data received by the seismometer network, Miller said the Corps and the NRC could roughly determine how many, and how large, of earthquakes could be expected in the lifespan of the dams built and of Wolf Creek, a nuclear power plant near Burlington.

Though Miller said the threshold of where a human can feel an earthquake is about 2.5 magnitude, some may feel smaller ones if they are located right on top of the epicenter. Miller said he KGS has enough seismometers across the state to detect any earthquake 1.8 magnitude or higher.

An increase in seismic activity in Kansas in recent years

The state network of seismometers has allowed KGS to continue monitoring seismicity in the state and Miller said, and in recent years the number of earthquakes began increasing.

Around 2014, Miller said horizontal drilling for natural resources like oil increased. Drilling produces wastewater which has to be disposed of somehow.

"(It's) pumping water into the deep rocks in the subsurface, right above what we call the basement or the Precambrian (layer)," Miller said.

This basement contains rocks that are several billion years old. Miller said putting this water in this location is a permanent solution because there is no economical way to filter or use the water because of the chemicals and dissolved solids in it.

Previously: Central Kansas feels rumble after Saline County earthquake

Disposal of fluids in this level has been going on for 50 to 70 years but has increased as horizontal drilling has also increased.

While Miller said the source of these earthquakes can't be proven, the working theory is that this increase of water disposal has also increased the pressures built up in this basement level.

There are existing faults near this level and when water is pumped into it, that water has to go somewhere.

"As the water pressure builds, you're pushing more and more water into faults that are in the granite, which is the Precambrian," Miller said. "What happens is that you have faults, that are already existing, already present, and they're critically stressed."

He said the plate tectonics of the Earth means these faults are constantly under pressure. The only thing keeping these pressures at bay and not causing the plates to move, which can cause earthquakes, is the pressure of the overlying rock pushing or "clamping" down on them.

As the pressure from the water increases, it has the opportunity to overcome this clamping pressure, lowering the threshold of energy needed to produce earthquakes.

"These faults that are present under Saline County, we know they're there," Miller said. "We know at some point in time they moved because that's what faults do."

Because of the presence of faults and the fact that they are constantly moving, Miller said these earthquakes were likely to happen down the line, but the thought is that the increased pressures from this water has induced them earlier.

"It probably would've happened...a hundred years, a thousand years (or) a million years, but we caused it to go early because we've changed the pressure in the sub-surface," Miller said.

He said that were common for disposal of water were fine, but as these pressures have increased over time, these practices may have more impact than they had before.

"It's like the straw that broke the camel's back," Miller said.

As mentioned, Miller said this can't be proven to be the cause of some of these earthquakes in Saline County and elsewhere in the state, but scientists know that earthquakes can happen by injecting fluid into the earth.

"The problem is we can't say 'this injector is causing this earthquake' because of what it did," Miller said. "It's a cumulative effect."

The KGS works with other state agencies like the Kansas Corporation Commission (KCC), which regulates well and injection sites, and the Kansas Department of Health and Environment, to look at where these sites are in conjunction to the tracked earthquake mapped-out faults.

"We just want to know, is there anything going on, unbeknownst to the operator or otherwise, that may be triggering these things," Miller said. "Some of the (earthquakes) may be natural, but some places, like the Saline County sequence, is not something we would expect, statistically, to see in a natural sequence."

Next steps for KGS come later this year

Miller said the survey isn't a regulatory agency and doesn't really travel to well and injection sites and relies on data collected by the KCC.

"We're pure science," Miller said. "The KCC has regulations that their operators all report their fluid... and disposal volumes annually. It's granulated down to what their volume was each month."

Miller said the KGS has developed a system to input on a map where earthquakes are, where operators are injecting and how much is being injected.

"We have all these data sets that are merged together," Miller said.

With 30 earthquake stations in the state that the KGS operates, the earthquake information is available quickly to the survey.

"What we don't have much in the way of detail is what's happening in terms of the industrial practices," Miller said. "The KCC usually gets the annual report of fluid injection from all the operators in March."

Miller said, because of the increase of seismic activity in the area, the KCC has asked operators to submit their reports early to get them as soon as possible.

This article originally appeared on Salina Journal: Saline County has seen an increase of earthquakes lately. Why is this?

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